Etiology:  Giardia muris is a flagellated protozoan.

Incidence:  The incidence of infection is rare.

Transmission:  Fecal-oral transmission via ingestion of infective cysts.

Distribution:  Giardia muris is found in the anterior small intestine.

Clinical signs:  No clinical signs have been attributed directly to these organisms. These protozoa may proliferate in diarrheic states, however their role as contributors to disease is poorly defined.

Diagnosis:

Antemortem: PCR of feces can be used to diagnose Giardia infection antemortem. Wet mounts of fresh fecal material or use of sucrose gradient may reveal cyst forms (difficult).

Postmortem: Wet mounts of intestinal contents may reveal slow-moving flagellated protozoa with a “falling leaf” rolling motility. Histopathologic examination may also be used to diagnose Giardia species infection.

Diagnostic morphology:  Broad, piriform trophozoite with 2 anterior nuclei that when stained with weak iodine solution gives the appearance of a “monkey face.” There are 8 caudally directed flagella.